Optical-fiber lighting unit having a movable lamp holder

ABSTRACT

Optical-fiber lighting unit, preferably intended for dental work, and comprising a casing (1) wherein there is provided an optical system (12) to which a plurality of optical-fiber conductors (27) are optically connectable via a light switch (26). The light switch (26) comprises an optical device, for example a lens (28), for focusing incident light, and is displaceable along a plane coinciding with an imaginary plane extending through the center axis of the optical-fiber light conductors (27), transversely of the light path from the optical system (12), to a number of positions corresponding at least to the number of end portions of optical-fiber light conductors (27) connectable to the light switch (26), and that the light switch (26) is thereby adapted to focus the light from a light source (11) provided in the optical system (12) to the end portion of at least one optical-fiber light conductor (27).

The invention of this application is disclosed in correspondingInternational Application No. PCTISE 82/00337, filed Oct. 18, 1982.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical-fiber lighting unit,preferably intended for use in dental work, and comprising a casing, inwhich there is provided an optical system to which a plurality ofoptical-fiber light conductors are optically switchable via a lightswitch.

2. Description of the Prior Art

The fiber optics technology is utilized in many different branches andincludes the transmission of light through long, thin fibers of glass orother transparent materials. The light is conducted through the fibersin a non-electrical manner by being reflected from wall to wall. No heatis transmitted or generated during this process.

In many types of precision mechanical work it is desirable, and oftencompletely necessary, that a large amount of cold light may be suppliedto a work area to enable the work to be performed correctly. Not leastfor dentists, this is a problem. It is difficult to obtain sufficientlight in the oral cavity and at the same time perform work on e.g. atooth. The dentist himself will often cause, with his body, hand ortool, shadowing of the light provided e.g by adjustable lamps and thelike. The teeth are in themselves uneven and are located unevenly inrelation to each other which for instance causes that parts of the teethwill be shadowed. Furthermore, it is difficult to get sufficient lightfor example into bores and at the innerside of the rows of teeth.

Various optical-fiber lighting units are presently commerciallyavailable, for example for use in diagnostics but above all for use indental work. These units are usually made with a space-consuming andheavy apparatus unit in which there are provided a transformer, a fanand a light bulb with a concave mirror. One or several optical-fiberlight conductors are connected by means of a coupling to the apparatusunit and are from there extended to one or several hand-held instrumentssuch as hand-mirrors, dental turbines or the like, to which thefiber-optics is connected by means of e.g clips. Mostly, it is necessaryto have several light conductors which can be mounted more or lesspermanently on some of the most frequently used dental tools, as forexample a high speed turbine, a low speed electrical motor and a probe.Due to the unwieldy design the unit must be placed comparatively faraway from the place of work, so that consequently also the optical-fiberlight conductors have to be made long, for instance 2-3 meters. Due tothe light losses in the optical-fiber light conductor, which losses mayattain a value of 50% per meter, the light bulb used in the unit mustadmit light of a high intensity and must therefore be a high-power lamp,which at the same time results in the lamp giving off much heat. As anexample, in a commercially available unit the light bulb has a power of150 W. One disadvantage of using such light bulbs are that they areshort lived-the manufacture of the optical-fiber lighting unit inquestion estimates the burning time to be 80-100 hours. Anotherdisadvantage is that the high emission of heat from the unit willinconvenience the dentist as well as the patient. Furthermore, acomparatively large fan must be used for cooling the unit and this fanintroduces disturbing noise into the work environment.

In the case where several optical-fiber light conductors, e.g. three,are connected to the same unit, all of them are activated, i.e they giveup light, even those that are not used for the time being. Usually thedentist only needs to use one fiber light conductor at the time, e.g.the one mounted on the turbine or the one mounted on a probe, whichmeans that the unit generates unnecessarily much light and heat, sincethe light bulb of the unit has to be dimensioned so that the light poweris sufficient for all three light conductors at the same time.

BRIEF SUMMARY OF THE INVENTION

The object of the present invention is to eliminate the above mentioneddrawbacks and to provide an optical-fibre lighting unit capable of amultitude of uses. It is of small size but despite this generates asufficient amount of light to a place of work via e.g. three differentoptical-fiber light conductors, each of which is switchable to the lightsource. The light admitted has to be a non-blinding, white cold light.Due to the small size of the optical-fiber lighting unit it may bemounted close to the place of work whereby the optical-fiber lightconductors may be made shorter than what would normally be the case,which decreases the light losses in the optical-fiber light conductorsand allows a smaller power of the light bulb to obtain a sufficientintensity of light at the place of work. Further objects are that theunit shall be simple to use, generate the least possible heat, and thatthe light bulb shall have a long burning time. This is attained in thatthe light switch comprises an optical means, e.g. a lens, for focusingincident light, said optical means being displacable along a planecoinciding with a plane extending through the center axes of theoptical-fiber light conductors, transversely of the light path from theoptical system, to a number of positions corresponding at least to thenumber of end portions of optical-fibre light conductors connectable tothe light switch, the light switch thereby being adapted to focus thelight from the light source provided in the optical system to the endportion of at least one optical-fiber light conductor.

BRIEF DESCRIPTION OF THE DRAWINGS

One embodiment of the invention will now be described in detail withreference to the accompaning drawings wherein:

FIG. 1 is a perspective view of an optical-fiber lighting unit accordingto the invention;

FIG. 2 is a horizontal cross-sectional view showing the optical-fiberlighting unit of the invention;

FIG. 3 is a cross-sectional view taken along the line III--III in FIG.2;

FIG. 4 is a cross-sectional view taken along the line IV--IV in FIG. 2;

FIGS. 5, 6 and 7 are diagrams which illustrate the theoretical path oflight in lens systems; and

FIG. 8 illustrates diagrammatically the "picture" which is focused onthe endportion of an optical-fiber light conductor.

DETAILED DESCRIPTION

FIG. 1 is a view of an optical-fiber lighting unit according to theinvention and intended mainly for dentists but also for otherprofessions with similar demands on lighting units. The optical-fiberlighting unit consists of an injection-moulded casing 1 of aluminum withplastic end walls 2a,2b. At one of the longer sides, an instrumentholder 3 is rotatably mounted on a base plate 4 for a lampholder 5.Various standard tools, such as e.g. a diagnostic probe 6 provided withoptical-fibre lighting may be hung onto the instrument holder 3. A rail8 fits into a slot 7 provided on one of the broad sides of theoptical-fibre lighting unit. By means of the rail 8 the unit may beconveniently and detachably mounted on a stand or a work bench near theplace of work. Instead of the rail 8 it would of course be possible touse magnets (not shown) for simple mounting of the optical-fiberlighting unit. Electrical power is supplied to the optical-fiberlighting unit via a cable 9 at a potential of e.g. 6 volts. Suitablelight intensity for each type of work may be adjusted by means of apotentiometer wheel 10.

FIG. 2 shows a view, partly in section, from the side of theoptical-fiber lighting unit with the upper half of the casing removed toillustrate the structure of details within the optical-fiber lightingunit. A halogen lamp 11 with a power of 20 W and mounted in a lampholder 5 is provided in the center of an optical system 12 comprising aconcave mirror 13 and a convex-convex condensor lens 14 secured in asleeve 15. The sleeve 15 in turn is secured co-axial with a firstcylindrical space 16 formed in the casing 1 in such a way, that thehalogen lamp 11 may be inserted through a hole 17 in the side of thesleeve 15. A further hole 18 is provided in the opposite side of thesleeve 15 and connects the inner space of the sleeve 15 with a hot airchannel 19 provided in the casing 1.

The hot air channel 19 extends along the complete longer side of theoptical-fiber lighting unit and permits hot air from the inside of theoptical-fiber lighting unit to escape through outlet openings or slots20 provided in the casing 1. The air is made to flow through thelighting unit by means of a fan 21 provided behind the concave mirror 13and in the extension of the same cylinder-shaped space 16 wherein theoptical system 12 is provided. Air is thereby sucked in through anopening 22 in the front end wall 2a, passes the fan 21 and the rear sideof the mirror 13 in through a channel 23 to a second cylindrical space24 formed in the casing 1, the passing air thereby cooling a circuitcard 25 provided with control electronics (not shown in details) forcontrolling the light intensity of the halogen lamp 11. Further, the airpasses past the lamp holder 5 and into the sleeve 15 where the halogenlamp 11, the mirror 13 and the condensor lens 14 will be exposed tocooling air. The air thereafter passes into the hot air channel 19 andout through the slots 20. Due to the low power, 20 W, of the lamp 11only a slight ventilation is necessary, but despite this, a working lifeof about 2,000 hours will be obtained for the lamp 11.

In the first cylinder shaped space 16 of the casing 1 there is provided,apart from the fan 21 and the sleeve 15, also a light switch 26, thepurpose of which is to focus the light from the halogen lamp 11 to oneof the ends of e.g. three possible optical-fiber light conductors 27a,27b, 27c. Only one at a time of the optical-fiber light conductors 27a-cmay transmit light from the optical-fiber lighting unit to an externalinstrument, i.e. only one conductor can be active whereas the other twoare inactive. The light switch 26 mainly consists of a plane-convex lens28, a metal slide 29, and a holder 30 which is also made of metal, andthe light switch is provided in the light path of the optical system 12.The plane-convex lens 28 is secured to the slide 29 which may beactuated manually by means of a control 31 to occupy one of threedifferent positions in the sidewards direction (seen from above). Aspring-loaded ball 32 arranged in the holder 30 co-operates with threeshallow holes 33a, 33b, 33c provided in one of the guide rails of theslide 29 and assures that the slide 29 will be retained by means of snapaction in the position to which it has been adjusted. Threethrough-bores 34a, 34b, 34c are further provided side by side in theholder 30 and are intended to receive optical-fiber light conductors27a, 27b, 27c which are pushed in through an opening 35 in the rear endwall 2b. Lock screws 36 are placed transversely of said holes 34 and areadapted to secure the optical-fiber light conductors 27 in place. Theends of the optical-fiber light conductors 27 are disposed in the focalplane 37 of he plane-convex lens 28, whereby maximum light transmissionis obtained to that optical-fiber light conductor 27 which at the momentis in the active position.

To obtain the largest possible light transmission, it is very importantthat the halogen lamp 11 is placed in the center of the optical system12, i.e. in such a manner, that a sharp image of the glow-wire 38 of thelamp 11 falls directly onto the end of that optical-light conductor 27which at the moment is adjusted into the active position. For thispurpose a base plate 4 is arranged at the middle of one of the longsides of the optical-fiber lighting unit and secured in the casing 1 bymeans of two screws (not shown). The base plate 4 is mechanicallyconnected with a movably arranged lamp support 41 by means of twotension springs 39 and four adjustment screws 40. A lamp holder 42 of aceramic material carrying the halogen lamp 11 is inserted into the lampsupport 41 which is made from a heat resistant plastic. The two springs39 are disposed at opposite sides of the lamp support 41 and tend topull the lamp support 41 closer to the base plate 4. One of the fouradjustment screws 40, which are made with semi-spherical ends, ispositioned in the center of the lamp support 41 on that side which facesthe base plate 4, whereas the other three adjustment screws 40 arepositioned symmetrically and peripherally around the central screw insuch a manner, that they form the corners of an imaging triangle. Thus,by means of the centrally located screw 40 the halogen lamp 11 may bedisplaced sideways transversely to the center axis of the optical system12, and by means of the other three adjustment screws 40 the halogenlamp 11 may be adjusted in an imaginary plane which cuts through, on theone hand, the center axis of the optical system 12 and on the otherhand, the glow-wire 38 of the halogen lamp 11.

The functioning of the optical system 12 and the light switch 26 isshown more in principle in FIGS. 5, 6 and 7. FIG. 5 illustrates a simpleoptical system including only one lens L1 the focal point F1 of which islocated at a certain distance from the lens. If a light source, e.g. alight bulb provided with a glow-wire (here symbolized by an arrow) isplaced between the lens L1 and the focal point F1, behind the lens L1(i.e. to the left of the lens), a virtual image B1 is obtained behindthe lens. With the aid of a further lens L2 placed at a distance infront of the lens 1 (see FIG. 6) this virtual image will be focused onthe end surface of an optical-fiber light conductor.

If the second lens L2 is displaced transversely to the light path of theoptical system (as illustrated in FIG. 7), the focused image of theglow-wire will consequently also be displaced, and in this way thedesired displacement of the light spot to an end surface of anotheroptical-fiber light conductor will be obtained.

The highest exchange of light from the light source 11 is obtained inthat concave mirror 13 and the lens 14 are arranged in relation to thelight source 11 in such a way, that the image B3 of the glow-wirereflected by the mirror is focused, mirror-reversed, just adjacent tothe "direct image B2" of the glow-wire at the end of the optical-fiberlight conductor 27 (see FIG. 8). A substantially spot-shaped orsquare-shaped light image will thereby be obtained which contributes tothe light exchange from the light source 11.

The invention is, of course, not limited to the embodiment describedabove, but a plurality of alternative embodiments are conceivable withinthe scope of the appended claims. Thus, instead of displacing the slide29 with the plane-convex lens 28 with respect to the holder 30 and thesleeve 15 with the optical system 12, it is conceivable to arrange thesleeve 15 and the plane-convex lens 28 as an integrated system and todisplace the whole of this in relation to the holder 30 with theoptical-fiber light conductors 27.

It is also concievable, instead of a single optical-fiber lightconductor 27 per inlet (hole 34), to arrange two or several per inlet,e.g. by pressing the ends of two optical-fiber light conductors 27against each other so that each conductor 27 will take the shape of thesurface of half a circle. In this way two or several conductors 27 maybe illuminated simultaneously, although the light switch 26 is in asingle position only.

I claim:
 1. In an optical-fiber lighting unit including a casing havingan optical system therein with a light source to which a plurality ofoptical-fiber light conductors are optically connectable, the end facesof the light conductors being aligned in an alignment line transverse totheir optical axes, the improvement comprising:a lens mounting meansslidably mounted within the casing for displacement along a pathparallel to the alignment line of the end faces of the light conductorsto a number of positions corresponding to the end faces of the lightconductors; and a focusing switch lens mounted in said mounting means,said switch lens being adapted to focus light from the light source ontothe end face of a respective light conductor, so that the light can besupplied to at least one light conductor at a given time via said switchlens.
 2. An optical-figer lighting unit as claimed in claim 1wherein:said light source comprises a glow wire; a mirror is provided onone side of said glow wire; and a lens is arranged at the opposite sideof said glow wire so that the image of the glow wire reflected by saidmirror is focused mirror-reversed adjacent the direct image of the glowwire at the end of the optical-fiber light conductor and a substantiallyspot-shaped light image is obtained.
 3. An optical-fiber lighting unitas claimed in claim 1 wherein:said lens mounting means comprises a slidearranged in the light path in front of a holder mounted in the casingwhich receives the end portions of the light conductors.
 4. Anoptical-fiber lighting unit as claimed in claim 2 wherein:said lensmounting means comprises a slide arranged in the light path in front ofa holder mounted in the casing which receives the end portions of thelight conductors.
 5. An optical-fiber lighting unit as claimed in claim1 wherein the light source comprises:a lamp holder; means for movablymounting said lamp holder in the casing for displacement in alongitudinal direction transverse to the light path of the opticalsystem; and angular adjusting means for angularly adjusting said lampholder relative to a center axis extending in said longitudinaldirection transverse to the light path of the optical system.
 6. Anoptical-fiber lighting unit as claimed in claim 5 wherein:said lightsource further comprises a base plate mounted on the casing; said meansfor movably mounting said lamp holder comprises a central adjustmentscrew rotatably mounted in said base plate and engaging said lampholder; and said angular adjusting means comprises a plurality ofadjusting screws rotatably mounted in said base plate and engaging saidlamp holder in spaced relationship around said central adjustment screw,and a plurality of tension springs operatively connected between saidbase plate and lamp holder for urging said lamp holder into engagementwith said screws.
 7. An optical-fiber lighting unit as claimed in claim1 wherein:the casing comprises two profiled interconnectable casinghalves which in their interconnected condition form two cylindricalspaces separated from one another; ventilating air inlet and slottedexit openings are provided through said casing; and openings areprovided between said spaces for interconnecting said spaces so thatventilating air may pass between the spaces and pass arond the lightsource and said optical system before it leaves the casing through saidexit slots in said casing.
 8. An optical-fiber lighting unit as claimedin claim 6 wherein:the casing comprises profiled interconnectable casinghalves which in their interconnected condition form two cylindricalspaces separated from one another; ventilating air inlet and slottedexit openings are provided through said casing; and openings areprovided between said spaces for interconnecting said spaces so thatventilating air may pass between the spaces and pass around the lightsource, said lamp holder and said optical system before it leaves thecasing through said exit slots in said casing.
 9. An optical-fiberlighting unit as claimed in claim 8 and further comprising:a blower fanmounted within one of said casing halves adjacent said ventilating airinlet for forcing ventilating air through said casing.